In general, a steering apparatus, which is connected with knuckles disposed on left and right wheels and steers the left and right wheels, is installed in an automobile.
FIG. 1 is a perspective view illustrating a steering apparatus for an automobile in the related art.
Referring to FIG. 1, a steering apparatus 5 for an automobile according to the related art is connected to knuckles 350 and 450 by means of tie rods 40 and 50 positioned at both ends, and adjusts leftward and rightward movement of axles 4 and 6, thereby enabling the automobile to be turned.
The steering apparatus 5 is mounted on a cross member 1 by bolting 7 at three points or four points. The cross member 1 is disposed to be elongated in left and right directions such that a left end is coupled to a left lower arm 2, and a right end is coupled to a right lower arm 3. Here, spring dampers for absorbing impact transmitted from a road surface to an automotive body through wheels are seated on and coupled to the left and right lower arms 2 and 3. That is, an upper end of the spring damper is connected to the automotive body, and a lower end of the spring damper is coupled to the lower arms 2 and 3, thereby absorbing shock when the automobile bumps.
Positions where the steering apparatus 5 is mounted on the cross member 1 are differently set in accordance with a shape or a structure of the steering apparatus 5, but generally, the positions are designed to be positioned at both ends of the steering apparatus 5 and at front and rear positions. Because performance of the steering apparatus 5 is dictated in accordance with the positions where the steering apparatus 5 is mounted on the cross member 1, detailed examination is required for the corresponding positions.
Because the currently applied cross member 1 is manufactured by a pressing process, the cross member 1 is thermally deformed due to welding. To maximally prevent shape distortion caused by the thermal deformation, various activities for managing quality are conducted, but it is difficult to implement a perfect shape. The positions where the steering apparatus 5 is mounted on the cross member 1 are vulnerable to the above described problem, such that forming may be applied to maximally reflect a designed shape, or a flat surface may be ensured by an additional process.
However, low mounting portion precision caused by a limitation of welding has an adverse effect on the steering apparatus 5, which is manufactured by high-precision processing, and consequently degrades performance. For example, in a case in which there is a difference in angle at a left surface of the left and right mounting portions, torsional force is applied to the steering apparatus 5 in a state in which the steering apparatus 5 is completely coupled to the cross member 1. The torsional force applied to the steering apparatus 5 affects the engagement between gears provided in the steering apparatus 5, thereby degrading steering performance because frictional force is increased when the steering apparatus 5 is operated.